The AW.15 Atalanta was designed to meet a 1930 Imperial Airways requirement for a four-engined airliner for its African lines, in particular for the service between Kisumu in Kenya and Cape Town, South Africa. The specification called for an airliner that could carry nine passengers, three crew and a load of freight for 400 mi (640 km), cruising at 115 mph (185 km/h) at 9,000 ft (2,740 m). Imperial Airways had decided to standardise on four-engined aircraft to prevent the failure of a single engine causing forced landings.[1] The prototype, G-ABPI, was named Atalanta and first flown on 6 June 1932,[2] by Alan Campbell-Orde from Whitley Abbey.

The Atalanta was a high-wing monoplane with four 340 hp (250 kW) Armstrong Siddeley Serval III ten-cylinder (two rows of 5 cylinders) radial engines. Its composite construction included steel, plywood and fabric; the undercarriage was fixed but was streamlined to minimize drag. The overall design of the aircraft was rather modern, and somewhat closed the performance gap between British and American airliners.[3]

The aircraft had few design flaws and any teething problems were quickly overcome. The prototype was flown to Croydon Airport for acceptance by Imperial Airways, and on 26 September 1932, it flew a commercial service from Croydon to Brussels and Cologne.[4]

The Atalanta could carry up to 17 passengers but Imperial Airways limited the seating to nine for the planes on the Indian route and 11 on the African route.

On 20 October 1932, the prototype was damaged in a test flight due to fuel starvation. Armstrong Whitworth was embarrassed by the accident and renamed the third production machine (G-ABTI, Arethusa) as Atalanta, hoping nobody would notice the swap.[5]

Two derivatives of the Atalanta were proposed: the Jaguar-powered AW.25 and Panther-powered AW.26, but neither left the drawing board.

Imperial Airways ordered eight aircraft which had all been delivered by 1933. The first service was flown from Croydon Airport to Brussels and then Cologne on 26 September 1932. The prototype G-ABPI left Croydon Airport on 5 January 1933 on a proving flight to Cape Town, South Africa. Three other aircraft joined it in South Africa to fly the service between Cape Town and Kisumu, although they proved to be too small for the traffic. On 1 July 1933, an Atalanta flew the first direct air mail service between London and Karachi. Two Indian-registered and two British-registered aircraft operated a Karachi-Calcutta service with was later extended to Rangoon and Singapore.

On 29 May 1933, G-ABTL flew through to Melbourne, Australia (arriving on 30 June) on a route survey flight.

Imperial withdrew the Atalanta from its African routes in 1937, with two being leased by Wilson Airways for operations in Kenya until July 1938. The African Atalantas were then transferred to India.[6]

Three aircraft were lost before the Second World War and the remaining five aircraft were taken over by BOAC. In March 1941, they were impressed into use by the Royal Air Force in India, being used to ferry reinforcements to Iraq in response to the Rashid Ali uprising.[6] In December 1941, they were handed over to the Indian Air Force for use on coastal reconnaissance duties, armed with a single .303 in (7.7 mm) machine gun operated by the navigator. The last patrol was flown on 30 August 1942 and the two survivors were transferred to transport duties where they continued in use until June 1944.[3][7][8]